Sheet separating mechanism of an auto document feeder

ABSTRACT

A sheet separating mechanism of an auto document feeding (ADF) device includes an ADF roller, two separating rollers and one pressing element. The pressing element is disposed between the separating rollers to form an assembly, and the pressing element and the separating rollers contact the ADF roller. A sheet is fed under the cooperation of the assembly and the ADF roller. The separating rollers rotate to provide a friction force for sheet separating. The pressing element presses a surface of the sheet such that the sheet may be smoothly fed without bulginess.

BACKGROUND OF THE INVENTION—FIELD OF THE INVENTION

The invention relates to a sheet separating mechanism, which is assembled in an auto document feeding device (ADF device) of an image input/output apparatus, by the sheet mechanism is at work, for separating a plurality of sheets such that the sheets may be sequentially fed into the auto document feeder.

BACKGROUND OF THE INVENTION—PRIOR ART

An ADF device is mainly composed of a sheet separating mechanism disposed at a sheet-feeding end of the ADF device, and a plurality of rollers disposed inside the ADF device. The rollers face the sheet separating mechanism. So, a sheet is separated from a plurality of sheets placed in a tray through the sheet separating mechanism, and is then moved forward by the rollers.

The sheet-feeding mechanism includes an auto document feeding roller (ADF roller) and a pad. A surface of the pad contacts the ADF roller, and the ends of the sheets are interposed between the ADF roller and the pad. Rotating the ADF roller in conjunction with a friction force between the pad and one of the sheets, the sheets may be separated and then fed.

The feeding orders of the sheets are different due to different position relationships between the pad and the ADF roller. For example, when the pad is located above the ADF roller, the bottommost one of the sheets is fed first. When the pad is located below the ADF roller, the topmost one of the sheets is fed first.

As shown in FIG. 1, a pad 11 is located above an ADF roller 12. Because the pad 11 is not combined with any pressing element, it cannot provide a reaction force on the ADF roller 12. So, a sheet 13 has bulginess 50 as it is moving forward.

U.S. Pat. No. 5,573,338 discloses a method of solving the problem of sheet bulginess. This method of this patent is to dispose elastic pieces at two sides and middle of the pad. Although the three elastic pieces can press the sheet to avoid the sheet bulginess, the elastic pieces and the pad must be assembled in the sheet separating mechanism after the procedures of assembling and fixing. Thus, the sheet separating mechanism has a complicated structure and cannot be assembled conveniently.

SUMMARY OF THE INVENTION

It is therefore an object of the invention to provide a sheet separating mechanism for an auto document feeder, wherein the sheet separating mechanism provides a pressing force on a surface of a sheet to prevent the sheet from bulginess.

Another object of the invention is to provide a sheet separating mechanism, which has a simple structure, for an auto document feeder.

The sheet separating mechanism according to the invention includes a separating roller, a pressing element and an ADF roller. The separating roller and the pressing element are assembled on a shaft to form an assembly facing the ADF roller. A sheet fed passing through a space between the assembly and the ADF roller will be pressed by the pressing element and not to occur the bulginess.

The separating roller of the invention replaces the conventional pad, and the separating roller may be driven by the ADF roller. The pressing element, which can press a surface of the sheet by its own weight or elasticity, includes a roller, a sponge substance or an elastic piece.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows a conventional pad combined with an ADF roller.

FIG. 2 shows a sheet separating mechanism according to the invention.

FIG. 3A is a cross-sectional view taken along a line A-A of FIG. 2.

FIG. 3B is another cross-sectional view taken along the line A-A of FIG. 2.

FIGS. 4 and 5 are schematic illustrations showing an auto document feeding state of the invention.

FIG. 6 is a schematic illustration showing a sponge cover serving as a pressing element of the invention.

FIG. 7 is a schematic illustration showing an annular brush serving as the pressing element of the invention.

FIG. 8 is a schematic illustration showing a presser structure serving as the pressing element of the invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT OF THE INVENTION

Referring to FIG. 2, a sheet separating mechanism of the invention includes an auto document feeding roller (ADF roller) 20, two separating rollers 30 and one pressing element 40.

The ADF roller 20 is axially fixed to a shaft 22. The shaft 22 connected to a power device for rotating the ADF roller 20. A shaft 32 passes through the two separating rollers 30, which are separated from each other. In addition, surfaces of the separating rollers 30 may contact the ADF roller 20. The pressing element 40 is disposed between the separating rollers 30. The shaft 32 passes through the pressing element 40.

FIG. 3A is a cross-sectional view taken along a line A-A of FIG. 2. The pressing element 40 is a roller defined as a pickup roller 42. The pickup roller 42 has a through hole 44, and the shaft 32 passes through the through hole. It is to be noted that the diameter of the through hole 44 is greater than the outer diameter of the shaft 32. So, the pickup roller 42 presses against the surface of the ADF roller 20 by gravity. When the shaft 32 rotates, the pickup roller 42 may properly swing or rotate by the friction force between the roller 42 and the shaft 32. At this time, the pickup roller 42 and the shaft 32 are not moved synchronously.

The separating rollers 30, the pickup roller 42 and the ADF roller 20 of the invention may be made of a rubber material or the pickup roller 42 may be made of a metal material.

FIG. 3B is another cross-sectional view taken along the line A-A of FIG. 2. The inner surface of the through hole 44 of the pickup roller 42 is formed with teeth 45. The surface of the shaft 32 is also formed with teeth 33. When the inner surface of the through hole 44 and the surface of the shaft 32 contact each other, the teeth 33 and the teeth 45 at the contact surfaces engage with each other, such that the rotating shaft 32 may synchronously rotate the pickup roller 42. In addition, the synchronous rotations of the shaft 32 and the pickup roller 42 may also be achieved by the sufficient friction force between the through hole 44 and the shaft 32. The so-called sufficient friction force may be provided according to rough surfaces, textures or materials.

FIGS. 4 and 5 are schematic illustrations showing an auto document feeding state of the invention. As shown in FIG. 4, a sheet 14 is located between the separating rollers 30 and the pickup roller 42. The sheet 14 contacts the separating rollers 30, the pickup roller 42 and the ADF roller 20.

As shown in FIG. 5, the ADF roller 20 moves the sheet 14 forward. At this time, the separating roller 30 and the pickup roller 42 press the surface of the sheet 14 to prevent the sheet 14 from bulginess.

It is to be appreciated that the pickup roller 42 movably covers the shaft 32 because the diameter of the axial through hole 44 of the pickup roller 42 is obviously larger than the diameter of the shaft 32. When the sheet 14 is moved forward, the pickup roller 42 presses against the surface of the sheet 14 by gravity, and the moved sheet 14 biases the pickup roller 42. Regardless of the relative rotation between the ADF roller 20 and the pickup roller 42, a relative displacement is formed between the biased pickup roller 42 and the ADF roller 20. Compared with the example disclosed in the '338 patent, in which no relative displacement is formed between the elastic piece and the ADF roller, the technology adopted in this invention is significantly different from that of the prior art.

FIG. 6 is a schematic illustration showing a sponge cover 46 serving as the pressing element 40 of the invention. The sponge cover 46 has the elasticity of resisting the external force so as to expand as it is pressed by the external force. In the configuration of the invention, the sponge cover 46 may be fixed onto the shaft 32 and the surface of the sponge cover 46 contacts the surface of the ADF roller 20. When the sheet is fed, the surface of the sheet 14 is pressed by the separating rollers 30 and the sponge cover 46, so the surface of the sheet is free from bulginess. In this embodiment, the sponge cover 46 and the ADF roller 20 are both rotatable.

According to the rotatable rollers 46 and 20, an annular brush 47 covers the shaft 32, and bristles of the annular brush 47 may smooth the surface of the sheet 14, as shown in FIG. 7.

Because the surface of the sponge cover 46 and the bristles of the annular brush 47 are both soft, it is defined that the external surface of the pressing element 40 has a soft portion 53.

As shown in FIG. 8, the pressing element 40 of the invention may be a presser 48 having one end 49 covering the shaft 32 and the other end 51 resting against the surface of the ADF roller 20. It is appreciated that the one end 49 of the presser 48 movably covers the shaft 32 such that the moving sheet 14 can move the other end 51 of the presser 48 as the sheet is being fed.

The invention mainly adopts the rolling separating roller 30 to replace the conventional stationary pad, and the pressing element 40 to cover the shaft 32 passing through the separating roller 30. The pressing element 40 may not rotate with the rotation of the shaft 32, but the relative displacement may be formed between the pressing element 40 and the ADF roller 20 such that the pressing element 40 can stably press the surface of the sheet 14. The pressing element 40 may also be rotated with the rotation of the shaft 32, and the soft surface of the rotating pressing element 40 presses the surface of the sheet 14.

The mechanism according to the invention has the following advantages.

1. The pressing element 40 can surely provide a stable and soft pressing force toward the ADF roller 20 regardless of the type of the pressing element 40. In addition, the separating rollers 30 can roll against the surface of the sheet 14. So, the invention can surely provide a pressing force on the sheet 14 as the sheet is fed, and the sheet 14 can be fed into the sheet separating mechanism smoothly.

2. The pressing element 40, such as a roller, a sponge cover, a brush or a presser, is very simple and available in the current market. Most important of all, the pressing element 40 and the separating roller 30 may be assembled on the same shaft 32 in a simple manner regardless of the type of the pressing element.

While the preferred embodiment of the present invention has been shown and described, it will be apparent to those skilled in the art that various modifications may be made in the embodiment without departing from the spirit of the present invention. Such modifications are all within the scope of the present invention. 

1. A sheet separating mechanism disposed at a sheet-feeding end of an auto document feeding (ADF) device, the mechanism separating a plurality of sheets from one another and feeding each of the sheets into the ADF device, the mechanism comprising: an ADF roller; at least two separating rollers disposed at a side of the ADF roller to face the ADF roller, wherein surfaces of the at least two separating rollers contact a surface of the ADF roller; and a pressing element disposed between the at least two separating rollers, wherein: the pressing element contacts the ADF roller by gravity; and when the sheet is fed, the at least two separating rollers and the ADF roller rotate, and the pressing element and the at least two separating rollers press against a surface of the sheet.
 2. The mechanism according to claim 1, wherein the pressing element and the at least two separating rollers are not moved synchronously.
 3. The mechanism according to claim 1, wherein the pressing element and the at least two separating rollers are moved synchronously.
 4. The mechanism according to claim 3, further comprising a shaft passing through the at least two separating rollers and the pressing element, wherein the shaft provides a friction force for moving the pressing element on contact surfaces between the pressing element and the shaft.
 5. The mechanism according to claim 4, wherein the friction force is provided by engaging teeth between the pressing element and the shaft.
 6. The mechanism according to claim 4, wherein the friction force is provided by contacting rough surfaces between the pressing element and the shaft.
 7. The mechanism according to claim 4, wherein each of the contact surfaces between the pressing element and the shaft is made of a material with a large friction coefficient.
 8. The mechanism according to claim 1, further comprising a shaft passing through the pressing element and the at least two separating rollers, wherein the pressing element is a pickup roller having an axial through hole, and the through hole has a diameter greater than a diameter of the shaft.
 9. The mechanism according to claim 1, further comprising a shaft passing through the pressing element and the at least two separating rollers, wherein the pressing element is a presser having one end movably covering the shaft and the other end pressing against the surface of the ADF roller by gravity.
 10. A sheet separating mechanism disposed at a sheet-feeding end of an auto document feeding (ADF) device, the mechanism separating a plurality of sheets from one another and feeding each of the sheets into the auto document feeder, the mechanism comprising: an ADF roller; at least two separating rollers disposed at one side of the ADF roller to face the ADF roller, wherein surfaces of the separating rollers contact a surface of the ADF roller; a pressing element disposed between the at least two separating rollers, wherein: the pressing element and the at least two separating rollers are moved synchronously, and the pressing element has a soft portion contacting the ADF roller; and when the sheet is fed, the at least two separating rollers, the pressing element and the ADF roller rotate, and the pressing element and the at least two separating rollers press against a surface of the sheet.
 11. The mechanism according to claim 10, further comprising a shaft passing through the pressing element and the at least two separating rollers, wherein the pressing element is a sponge cover fixedly covering the shaft.
 12. The mechanism according to claim 11, wherein a surface of the sponge cover serves as the soft portion.
 13. The mechanism according to claim 10, further comprising a shaft passing through the pressing element and the separating rollers, wherein the pressing element is an annular brush fixedly covering the shaft, and the annular brush has projecting bristles on a surface of the annular brush.
 14. The mechanism according to claim 13, wherein the bristles serve as the soft portion. 